The invention relates to methods and apparatus for sterilization of ophthalmo-logical instruments, and more particularly to sterilization methods and apparatus for reducing outbreaks of diffuse lamellar keratitis.
Diffuse lamellar keratitis or DIX (also referred to as xe2x80x9cSands of the Sahara keratitisxe2x80x9d) is a recently recognised post-surgical condition involving an inflammation that occurs in laser corneal surgery patients. This condition is typically associated with the LASIK surgical procedure (Laser Assisted In Situ Keratomileusis), the most rapidly increasing laser corneal surgery procedure in North America. It usually occurs in the first few days postoperatively. In LASIK surgery, surgeons cut a flap of the cornea and fold it back to expose the layer below, which is shaped with the laser to correct the patient""s vision. The corneal flap is then put back in place. The DLK condition, an inflammatory. infection, can develop under the corneal flap and can threaten the patient""s sight. DLK usually responds to intensive topical steroids, with lifting of the flap and irrigation in more advanced stages. Untreated or severe cases may progress to melting of the flap with the potential for significant loss of vision. It can occur at low levels in some surgical clinics, however, massive outbreaks have also occurred, where 30-80% of patients receiving the surgical procedure at a clinic may be affected. To date the cause of the complication is not known. Some authors have suggested deposits from the microkeratome blade as a cause of DLK. Others relate DLK to particles from the eye drape. Since the use of laser surgery to correct vision is a relatively new technique which is seeking to be generally accepted, it is important that outbreaks of this inflammation be prevented or at least minimnized.
The present inventors have discovered a method and apparatus to reduce outbreaks of the DLK inflammation. Instrument sterilizers are used to prepare surgical materials for the LASIK procedure. These sterilizers have a holding tank, or reservoir, that supplies water to be turned into steam for the sterilization. If these holding tanks become contaminated with specific biofilm bacteria they can become a source of certain toxins (lipopolysaccharide or endotoxin) that can be released into the sterilizer system and deposited on the surgical instruments that are to be used in the delicate structures of the eye (corneal stroma). These toxins are extremely heat stable (400xc2x0 F. for 4 hours is required to destroy them) therefore they are not destroyed by the short sterilization cycles provided by the sterilizers in these surgical clinics. As a result of this it is imperative to remove these biofilm bacteria from the reservoirs and to keep the reservoirs free of subsequent contamination by biofilm bacteria.
The present invention therefore provides a method to remove biofilm bacteria from the reservoirs in these sterilizers, a method to prevent biofilm bacteria from contaminating the reservoirs, and an external reservoir that may be fitted on existing sterilizers, by-passing the existing internal reservoirs, that is simple to use and on which it is very easy to conduct preventative anti-bioflim procedures.